SOLID SOLUTION HEAT TREATMENT FOR WELDED STAINLESS STEEL PIPE

摘要

PURPOSE:To prevent occurrence of high temp. embrittlement cracking, by controlling tension so that stress quantity in steel pipe longitudinal direction caused by tension applied to steel pipe becomes to a specified value corresponding to steel kind in solid soln. heat treating furnace, at said treatment of seam welded steel pipe. CONSTITUTION:An austenitic stainless steel pipe 7 welded and shaped by a welding torch 1 is solid soln. heat treated by a solid soln. heat treating furnace 3. In this time, speed meters 8, 8a of roll revolution mode are arranged before and behind the furnace 3 and connected with a control panel 9, stress quantity calculated by a prescribed formula is fed back to a pinch roll 5 by the panel 9 and revolution of the roll 5 is controlled according to the stress quantity. Namely, tension applied to the pipe 7 in the furnace 3 is controlled so that stress quantity of the pipe 7 in longitudinal direction is controlled to =4.0% in SUS304 steel pipe, =3.0% in SUS3041 pipe, =1.5% in SUS316 pipe, =1.0% in SUS3161 pipe and =0.5% in SUS310 pipe.